Dragster 7.65 175 mph , I had convertor adjusted from 6000 to 6400 will that change 1/4 mile finish line rpm. Also tire rollout of 106 to 104 how much rpm difference will that make approx .

The stall will raise it and the roll-out will increase it so also, maybe 300-400 rpm at the stripe?

The new shorter tire will make the new converter more efficient. So to forecast the new finish line rpm you'd need to know the old finish line rpm. Then you figure the tire growth at 20% and do the equation to come up with the current converter efficiency (slippage). Then to forecast the new finish line rpm, it'll come down to how much more mph the car has at the stripe and the converter efficiency. So really the better question in accurately forecasting the new finish line rpm is,,, how much more speed will the car have at the stripe with the new gear (shorter tire) and new looser converter. An engine dyno sheet will give a good indicator on the amount of speed increase is possible depending on how much power was being isolated below the new TQ stall, 6400 rpm. If any.

This message has been edited. Last edited by: Mike Rietow,

Car goes 7250 rpm in the lights. Don't want to put the shorter tire on if the looser convertor is going to put the rpm up already

just trying to pick up a bit of ET

My way would be .04 at best,doing both mods.this of depends on many variables.

Decent 565. I guess 7500 to 7600 wont hurt it

Without getting technical my way on rpm would be 7650 and unless it's a dump truck motor should be fine

The converter was slipping around 7% before. See what you end up with in the new converter at the stripe. There is room for improvement from 7% if my calculations with limited info are correct. The rpm could be lower than you might think if the new converter is 1% o 2% more efficient even with more speed. You could test heavier oil too. Hypothetically speaking at 177mph, the rpm at the stripe is 7450 with 5% slippage.

This message has been edited. Last edited by: Mike Rietow,

I would bet (not much thou...) no change on the tach or slip.